Two weeks ago Maria del Carmen Garcia, a Spanish woman in her 60s, went to jail. She had killed a man in 2005, this was her punishment.

But justice is a funny thing and it is tied, more tightly than we sometimes like to admit, to revenge. The line can be blurry, not least because we have such an odd relationship with what is a very basic human response. Vengeance is uniquely human.

In 1998 Maria del Carmen Garcia sent her then 13-year-old daughter to buy bread in the middle of the day. Antonio Cosme Velasco, then in his early 60s, raped the girl at knife point, was captured a few days later and on a plea bargain was sentenced to nine years in jail. In 2005, during a three-day release, he returned to their small village outside Valencia and when he passed Maria del Carmen in the street he smirked and asked how her daughter was, before disappearing into a bar. A short while later Maria del Carmen arrived in the bar with a bottle of petrol, she threw it over her daughter’s rapist and set him on fire. He died 11 days later of his injuries.

The legal wranglings around Maria del Carmen’s mental health at the time of the attack have taken this long. Many people feel that not only is a custodial sentence not appropriate, but that it is not merited. It has been argued that she was provoked, that it was a spur of the moment action rather than premeditated, that the circumstances were exceptional, that she was within her rights as a parent and that she did the world a service. But the law in Spain, as in Ireland, says you are not allowed to make your own justice. There are questions of degree and objectivity, but there is also the inference that justice without the ministrations of a prescribed system is vengeance, and vengeance is wrong.

For centuries the moral high ground has held that revenge is bad. Jesus said to turn the other cheek, Marcus Aurelius said the best revenge is to be unlike he who performs the injury and Gandhi said an eye for an eye ends up leaving everyone blind. There is, unquestionably, wisdom in this, but is it universal wisdom? Does it always hold true?

And if it’s the case, why do we so love a nice tale of revenge? From Homer’s Iliad to Dante’s Inferno via Hamlet through to Spartacus, Kill Bill, Unforgiven and the hit TV show Revenge, we like stories of retribution.

Then there are the urban myths and real life classics that have gone down in history and tickled our moral debates. There are the fairly harmlessly unpleasant paybacks to errant lovers like leaving seafood to rot in their curtain rails, selling their prized possessions for very little money on eBay or slashing their wardrobes of expensive clothing. Then there are the more criminally minded. In 1993 John Wayne Bobbett came home drunk and raped his wife again. But this time she went to the kitchen, got a knife, cut off his penis, jumped in her car and drove off, throwing the severed organ out of the car window. It was later found and reattached, something John Wayne made use of in his subsequent porn career. Lorena Bobbett was found not guilty by virtue of temporary insanity.

In 2006 Anthony Stockelman was sentenced to life for the murder of ten-year-old Katie Collman. The sentence was not harsh enough for some and in jail Stockelman had “Katie’s Revenge” tattooed on his head by other inmates. Perhaps they had been inspired by Jackie Clarke the year earlier who invited the man who had raped her to her home. She drugged him, her 19-year-old son tied him up for her and, after beating him around the legs with a baseball bat, she tattooed “rapist” on his penis with a needle and ink.

And what is war, most often, if not a series of acts of revenge? Apart from the moral high ground suggesting revenge is wrong, research also indicates that acting on desires for revenge does not deliver nearly as much satisfaction as we imagine. PET scans reveal that the during the decision to take revenge there is heightened activity in the reward centre of the brain, so on one very basic level we really do like getting our own back, but, after committing acts of revenge many people express remorse.

This Revenge Paradox’ is thought to come about because of the rumination factor, essentially that afterwards we think about it for longer, give it more importance and sometimes feel bad. People who do not take revenge tend to get over things more quickly, in part, it is thought, because they are more likely to minimise the damage of the original offence in order to move on.

However, not all revenge is made equal.

There are all kinds of factors that change how we feel about revenge and the degree of satisfaction we take from it. For a start there are different personality and societal factors that affect how and why we feel the need for retribution.

An Australian study in 2008 found that vengeful tendencies were highest in groups leaning towards right-wing authoritarianism and social dominance. Which is no great shock given that really, if we are to break it down very simply, revenge falls into two categories. There is ego-based revenge, where people feel humiliated, like they have lost face, their honour has been slighted, their pride has been scuffed and they feel an act of revenge will restore this lost honour. Then there is justice-based revenge, people feel a wrong has been done, an unfairness committed and they want to make someone pay for that.

These are two very different ideas. Vengeful personality types tend to be motivated by power and status and in the Australian study it was conservative, right-wing people with a deference to authority and respect for traditions who were most in favour of notions of revenge and retribution.

People with a less traditional view, people who tend towards a view of the world as a more universally connected place, tend to be less in favour of revenge. Influenced perhaps by notions like karma, these people tend to think that actions of revenge tend to lead nowhere good.

An American study found that cultural factors reinforce the differences. Certain societies value saving face over, for instance, freedom, so cultural differences alter people’s perceptions of how great an insult is and therefore what kind of retribution is required.

It also sometimes even alters people’s perceptions of whether or not an insult or offence has been committed. Taking offence, more than beauty, is in the eye of the beholder.

ABC show 'Revenge'

Conservative, authoritarian societies and the people who support them tend to be less forgiving which is why it is often deemed acceptable to torture and kill people who are considered to have committed an offence against honour and pride. This is why a society might deem it acceptable to stone a woman to death for adultery, to punish a woman for being raped, for family members to kill a girl they think has brought shame on the family, for parents to put their pregnant daughter in a Magdalene Laundry and never let her out.

Although difficult to study, it seems that the rumination factor that can retrospectively diminish the pleasure of getting your own back for individuals does not apply in groups where the justice system is revenge-based.

pleasure

Guilt and regret are largely learned emotions, they are not instincts so the rumination factor that diminishes the pleasure of acts of revenge is a learned moral, not something intrinsic. Since the beginning of time we have been fascinated by and sought revenge, on a basic level we really enjoy it, but we’ve long been told it was wrong. An instinct, a great pleasure but morally wrong, which was, still is in some quarters, the teaching on sex.

Several studies have found that the only time people do feel satisfaction from acts of revenge is when the offender knows exactly why they are being punished. There is also some evidence that revenge is best served cold rather than as a kneejerk reaction.

There’s a big difference between vindictiveness and vengeance just as there is a big difference between justice and control.